The invention relates to a filter press with a press frame to support filter plates movably along the longitudinal axis of the press frame, where the filter plates are oriented at right angles to the longitudinal axis of the press frame and connected to one another, and where a pressure plate is provided that can be moved along the longitudinal axis of the press frame by means of pushing or pulling equipment and which presses the filter plates against one another during the filtration process.
Filter presses of this kind are used to separate solids from the liquid phase of a suspension to be filtered. This filtration process takes place in the filter plates, where several filter plates are joined to one another to form a filter plate assembly. With the aid of a closing cylinder, usually a hydraulic closing cylinder, pressure is applied to the filter plate assembly in order to guarantee the necessary leak-tightness between the individual filter plates. Each of the filter plates has a filter area covered with a filter cloth, where the suspension to be filtered is pressed into the filter chamber formed between two filter plates and against the filter cloth. The filtrate between the filter cloth and the filter area is then carried off, and the filter cake remains in the filter chamber. The filter cake drops out when the filter plates are separated from one another.
In some applications, for example in mining, the cycle times are very short, which means that closing of the filter plate assembly, filling with the suspension to be filtered, the filtration process itself, opening of the filter plate assembly, discharge of the filter cake, and washing of the filter cloths all have to proceed relatively quickly, often within a few minutes. A delaying factor here is opening and closing of the filter plate assembly. In order to accelerate this process, the filter plates are connected to one another using chains, for example, so that the entire filter plate assembly is pulled apart when the outermost filter plate is moved and the entire filter cake can drop out. Compared with moving one filter plate after another, this method requires a longer filter plate travel path. According to the state of the art, the closing cylinder, for example, is also used to pull the filter plate assembly apart, however this entails some disadvantages. If the closing cylinder is used, for example, the press volume is limited because only one limited cylinder stroke can be realized. A long cylinder stroke also necessitates large quantities of oil and exposes large areas of the closing cylinder piston rod to contamination from falling filter cake. In addition, there are also disadvantages from radial forces and other unfavourable loads on the piston rod, the piston, and the respective seals. Lastly, opening and closing the filter plate assembly using the closing cylinder takes considerable time because the closing cylinder is designed for high closing pressure, but not for rapid piston movement.
Thus, attempts were also made to provide additional hydraulic drives for opening and closing the filter plate assembly and which were designed for a long and rapid cylinder stroke. The correspondingly thin piston rods, however, cause problems due to their low mechanical loading capacity, and it is often necessary to use several additional hydraulic drives of this kind, which have to be controlled exactly however, in order to ensure synchronous movement. Ultimately, these systems also do not solve the problem of long piston rods and their being contaminated by falling filter cake.